FIELD-EVALUATION OF THE EPA (KENAGA) NOMOGRAM, A METHOD FOR ESTIMATING WILDLIFE EXPOSURE TO PESTICIDE-RESIDUES ON PLANTS

The Kenaga nomogram was developed by the U.S. Environmental Protection Agency (EPA) in the mid 1970s and has since been used prior to the re gistration of a pesticide to estimate the maximum potential pesticide residue level on plant material in the food chain of wildlife. The obj ective of this study was to evaluate the nomogram using field data. Si x pesticides representing a variety of pesticide classes were applied to 15 plant species. Five of the six nomogram categories were tested w ith plant parts representing differences in surface morphology (i.e., glabrous vs. pubescent leaves). The sixth category was a mixed-grass c ommunity seeded with three grass species. Pesticide residue levels wer e determined the day of application and up to 32 d afterward. While th e linear nomogram model does not represent the data as well as other m odels, relatively few data points (10%) collected on the day of pestic ide application exceeded the nomogram predictions. The one systemic pe sticide tested had degradation rates similar to nonsystemic pesticides in most categories. Present nomogram categories were significantly di fferent from each other in most cases. However, the forage category sh ould be combined with the leaves and leafy-crop category and have high er estimated residue levels than the Kenaga nomogram. A considerable a mount of variation occurs in the level of pesticide residue on plant m aterials even under controlled experimental conditions and therefore n omogram values should be used as an estimate only until actual field r esidue data are available. The nomogram, with modifications, appears t o be a reasonable regulatory device if careful thought is given in sel ecting the plant category for making residue estimates.